Plantae

Plantae is a major kingdom of eukaryotic, multicellular organisms that are predominantly photoautotrophic. Members range from simple mosses to large trees and include many aquatic algae that are closely related to land plants. Traditionally, Plantae encompasses land plants (embryophytes) and a broad array of green and other algae; in modern systematics, it is commonly treated as the group that descended from a primary endosymbiotic event that gave rise to chloroplasts in the lineage.

Key characteristics include cellulose-based cell walls, chloroplasts containing chlorophyll a and b, and storage of starch. They are predominantly non-flagellated in adult form, though some algae and spores are motile. Most develop from embryos protected by parental tissue (embryophytes). They show tissue differentiation and, in vascular groups, lignified transport tissues enabling greater height.

Major lineages: bryophytes (mosses, liverworts, hornworts); pteridophytes (ferns and their relatives); gymnosperms (conifers, cycads, ginkgo); and angiosperms (flowering plants). In many classifications, algae that are closely related to land plants are included as part of Plantae, while others separate them. Reproduction often features alternation of generations, with distinct haploid and diploid phases; seeds and flowers are key innovations in the angiosperms.

Ecology and human relevance: as primary producers, they form the base of most ecosystems, fix carbon, and release oxygen. They build soils, create habitats, and are essential sources of food, fiber, medicines, and ornamentals for humans worldwide.